GPU usage spikes

I've noticed that when playing some games like New Vegas and Torchlight 2, the GPU usage would be very erratic. GPU usage is low for these two games, jumping from 0 to 30ish %.

OC is stable at 1100 / 1300 MHz but the clocks would alternate between base clock and overclock. (Meaning from 1100 MHz core clock down to 900 MHz then back up again). However, temperature rarely goes above 60c and I don't notice much stuttering when playing these games.

This does not happen in other games I am also playing / have played.

My question is: Is this GPU usage and clocks going all wonky bad for the GPU? I actually don't have any trouble playing New Vegas, game is pretty smooth and temp stays in the mid 50c. But I am afraid playing under these conditions would somehow damage my GPU.

I've installed mods for both of these games. Upon disabling the mods for Torchlight 2, the GPU usage seems to be more normal. Clocks have also become stable. Enabling in game Vsync causes the GPU usage to spike even more.

I've ran plenty of stability tests on my overclock. So I am fairly certain that it's stable. I've played far more demanding games like Witcher 2, sleeping dogs, Tomb Raider, all without any GPU throttling or anything like that. Nothing goes wrong or anything like that either when running 3DMark 11 and Unigine Heaven benchmarks.

I am thinking it's just game engine.

But what I really want to know is if these GPU spikes / throttling can potentially harm my gpu.